The present invention is directed to a laser diode with an electrically tunable emission wavelength having a TTG-DFB (tuneable twin guide-distributed (feedback) structure. p The TTG-DFB laser diode of European Patent Application EP 0 360 011 is considered especially suitable for utilization in future optical communication transmission systems because of its broad, continuously variable tunability of the emission wavelength. Its employment, for example, as a local oscillator in optical heterodyne receivers is promising. In this laser diode, an active layer and a tunable layer are arranged vertically one above the other and separated by an intermediate layer, whereby separate current injections into the tuning layer and into the active layer can occur via lateral regions and through the intermediate layer. In prior art embodiments this TTG-DFB laser diode is constructed on a p-doped substrate. One of the two critical laser layers, i.e. the active layer or the tuning layer, is electrically driven via the substrate depending on which layer is located on the side of the intermediate layer facing toward the substrate. The substrate must therefore be electrically insulated from sub-carriers that are to be frequently equated with the electrical ground, this requirement increasing the manufacturing outlay.